Classifications

• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21C—NUCLEAR REACTORS
  • G21C21/00—Apparatus or processes specially adapted to the manufacture of reactors or parts thereof
  • G21C21/02—Manufacture of fuel elements or breeder elements contained in non-active casings
  • G21C21/04—Manufacture of fuel elements or breeder elements contained in non-active casings by vibrational compaction or tamping of fuel in the jacket
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E30/00—Energy generation of nuclear origin
  • Y02E30/30—Nuclear fission reactors

Definitions

• This invention relates to a method of making uniform close-packed dispersions of different materials within zones or layers within a container. More specifically it relates to a method for making nuclear fuel rods containing both fuel and blanket material by vibratory compaction in which the fuel and blanket material are situated in separate zones within the fuel rod with a minimum of intermingling between the zones of different material.
• This type of reactor known as a breeder reactor-commonly has a blanket of fertile material such as uranium-.238 or thorium- 232 surrounding a fissionable-fuel-material core. This blanket material absorbs neutrons which are emitted from the fuel and is partially converted into plutonium- 239 or uranium-233 which are fissionable. This fissionable material from the blanket can then be processed, concentrated and used as fuel material.
• a fuel rod for such a reactor may, for example, consist of a distinct zone containing blanket material, above which in a distinct zone is the fuel material, and above this is the second or upper blanket zone. There should be no intermingling between the materials in each zone.
• Advanced nuclear reactor designs can use fuel and blanket material in the form of small spheres which are compacted within the fuel element.
• the density of the fuel elements can be controlled to very close tolerances.
• Vibratorily compacted fuel elements are usually formed using several different size components to obtain a fuel element of controlled, high density.
• the density is dependent upon the amount of void space between particles.
• perfect spheres could be used, in which case the space between spheres can be filled with smaller spheres to increase the total density and the space between the smaller spheres can be filled by a still smaller component to increase the density still further.
• precalculated quantities of different materials which are the same relatively large diameter are added to a container in succession and the container is vibrated to compact the material into layers within the container.
• successive amounts of smaller diameter material are added to the container in the same order as that material already in the container and compacted by vibrating this smaller diameter material into place.
• the amount of smaller diameter material which is added is an amount precalculated to just occupy the space remaining in the layer of the same material.
• the method of the invention consists of precalculating the amount of relatively large diameter material which is to form the first or lowest layer or zone in the container to be packed. This large diameter material is then added to the container while driving the container with a vibrator in order to pack the material into the layer. This same procedure is then followed for each succeeding layer, each time using material of approximately the same relatively large diameter to form each layer within the container while maintaining the vibration.
• a predetermined amount of a smaller selectedsize-range of the same material as the first or lowest layer is introduced into the container through the thimble 3 screen while continuing the vibration.
• this smaller diameter material has sifted through the material in the container into the lowest layer and is completely packed therein, relatively smaller diameter material for each succeeding layer may be added to the container in order and vibrated into place to form a dispersion of different materials in sharply defined layers within the container.
• the density of the container may be increased by the use of material of a still smaller diameter which would be added in the same manner as just described, as it would act to decrease still further the void fraction of the container.
• the vibratory compaction can be carried out using a device similar to that described in the before-mentioned patent. This includes use of a pressure thimble to hold each succeeding component in place and a rattle cage to prevent bridging of the various components. It was found that a simple electromechanical vibrator operating at 60 cycles was able to provide adequate axial vibration to compact the components. Transverse shock or vibration to prevent bridging is imparted to the container by the rattle cage placed over it which bounces back and fourth against the container side because of the axial vibration.
• the vibration time was found to be dependent upon the diameters of the spheres being used. It was found that the ratio of sizes determines the rate of entry or rate at which the second component will move through the void spaces between the first component spheres. Thus, the higher the ratio of sizes, the faster the rate of entry and the less vibration time which was required to obtain distinct lines of demarcation at the interface be tween two layers of different material.
• a further advantage in making zoned fuel elements by the method just described is that a large number of rods can be filled and vibrated at the same time on a single piece of equipment.
• the amount of first component blanket material necessary is dependent upon the diameter of the fuel rod, the height of the blanket section of the rod and the diameter of the fuel material being used. This can be determined by first finding the packing eificiency, or void packing efiiciency, which is the fraction of available void volumes which is occupied by the entering solid material. This may be found by the following equation for the first component:
• D is the inside diameter of the tube
• d the diameter of the spheres Within the same tube
• e the base of natural logarithms.
• the Weight of the first component charge may be determined by the following equation:
• W is the weight of the spheres
• V is the volume of the container per unit length
• G is the density of the spheres
• Pe is the packing efficiency
• L is the length of the particular fuel or blanket zone being filled.
• the calculated charge for the second component can be determined by:
• V is determined from V (l-Pe
• EXAMPLE I A binary dispersion was made in a glass tube of cylindrical cross section having an internal diameter of 0.276 inch, using copper shot to simulate blanket material and steel shot to simulate fuel material in order to determine the amount of intermingling. Each blanket zone had a length of 11.8 inches. The largest or d spheres had a diameter of 0.086 inch. Solving the equations given below, the calculated first component blanket charge was 56.83 grams. The second component blanket charge had a diameter of 0.015 inch. The calculated charge of this second component material was 18.2 grams.
• the fuel zone was 23.01 inches in length with a first component fuel diameter of 0.086 inch and the calculated charge of steel shot was 101.8 grams.
• the second component fuel zone shot was 0.009 inch in diameter and the required charge was calculated to be 42.0 grams.
• the upper blanket zone was of the same length as the lower zone so that the amounts of calculated first and second component needed were the same as for the lower blanket zone.
• the rod was packed using the apparatus previously described.
• the first component blanket material was added to the rod first, followed by the first component fuel material and then first component blanket material again, each material being vibrated for 10 minutes before addition of the next material.
• Second component blanket material was added next after replacing the pressure thimble with one having smaller diameter holes to prevent the first component material from shifting.
• This second component was precalculated using the above equations and added to the fuel rod while continuing to drive it with the vibrator. Once all of the component was added, vibration was continued for 15 minutes to ensure complete compaction. In the same manner, the second component fuel and blanket material, each being vibrated for 15 minutes after addition to the rod, was completed to obtain complete packing.
• second component material was added to fill each Zone up to the level of the first component material and any excess not used or additional amount needed was used to calculate the deviation of the total charge from the calculated charge.
• the deviation amounted to no more than 2.5% of the total charge for each zone.
• the calculated density was 73.5% for the upper and lower blanket sections and 79% in the fuel section.
• EXAMPLE II just occupy said interstices within said first blanket material, subjecting said tube to axial and transverse vibration,
• the fuel tube and shot diameters are the same as given d i ll repeating h procedure with predeter. 1n the PI'BVIOHS p
• the blanket length was 10-89 mined amounts of fuel material and blanket material of inches for both upper and lower blanket zones w th a id same smaller size, 21.78 inch fuel zone section.
• the tube was loaded in the 2.
• the method of claim 1 wherein predetermined same manner as the tube in the previous example.
• the amounts of still-smaller-diameter material are sequential results and differences between the calculated and actual ly added to said rod in the same orders as said larger material used are given in Table II.
• a method of preparing a fuel element for a nuclear reactor comprising: introducing a predetermined amount of blanket material of predetermined size into a tube, vibratorily compacting said blanket material, introducing a predetermined amount of fuel material of the same predeterimned size range into said tube, vibratorily compacting the fuel material, introducing a predetermined amount of blanket material of a pretermined smaller size range into said tube, vibratorily compacting said blanket material, restraining said materials from axial terial and said predetermined amount being of sufficient quantity to just occupy the interstices of the same material, and vibratorily compacting said still-smaller-diameter material.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Manufacturing & Machinery (AREA)
• Plasma & Fusion (AREA)
• General Engineering & Computer Science (AREA)
• High Energy & Nuclear Physics (AREA)
• Solid Fuels And Fuel-Associated Substances (AREA)
• Fuel-Injection Apparatus (AREA)
• Crushing And Grinding (AREA)

Applications Claiming Priority (1)

Publications (1)

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ID=24549819

Family Applications (1)

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Cited By (1)

Citations (2)

• 1967
  • 1967-04-28 US US635961A patent/US3517431A/en not_active Expired - Lifetime
• 1968
  • 1968-03-14 GB GB12567/68A patent/GB1151326A/en not_active Expired
  • 1968-04-03 SE SE4397/68A patent/SE333199B/xx unknown
  • 1968-04-16 BE BE713717D patent/BE713717A/xx unknown
  • 1968-04-19 FR FR1576445D patent/FR1576445A/fr not_active Expired
  • 1968-04-27 DE DE19681758238 patent/DE1758238A1/de active Pending

Patent Citations (2)

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